Pulse oximetry generally refers to non-invasive techniques for monitoring the oxygenation of hemoglobin in an individual's body, such as a human body. Pulse oximeters are typically used when an individual's oxygenation may be unstable. For example, pulse oximeters can be used in intensive care settings, emergency room settings, operating room settings, recovery room settings, and for pilots who operate unpressurized aircraft. Pulse oximeters can also be used for mountain climbing, and by athletes whose oxygen levels can decrease at high altitudes or with exercise.